small typo in the packages method

Small typo that breaks the packages method

Author: aaronlippold

libraries/linux_updates.rb

@@ -55,7 +55,7 @@ def uptodate?
   def packages
     return [] if @update_mgmt.nil?
     p = @update_mgmt.packages
-    return [] if p.nil? || u.empty?
+    return [] if p.nil? || p.empty?
     p['installed']
   end